Hard disk drives (HDD) have been increasing the recording density of the magnetic disks on which data storage occurs. Correspondingly, the thin-film magnetic heads used to write and read that data have been required to improve their performance as well. The thin-film read/write heads most commonly in use are of a composite type, having a structure in which a magnetic-field detecting device, such as a giant-magnetoresistive (GMR) read sensor is used together with a magnetic recording device, such as an inductive electromagnetic coil. These two types of devices are laminated together and mounted on a rectangular solid prism-shaped device called a slider. The slider literally flies over the rotating surface of a disk while being held aloft by aerodynamic forces at a height called the fly height (FH). The read/write head is mounted in the slider where it serves to both read and write data signals, respectively, from and onto magnetic disks which are the usual magnetic recording media in a HDD. Typically, the magnetic writer portion of the read/write head is a small electrically activated coil that induces a magnetic field in a magnetic pole. The field, in turn, emerges at a narrow write gap (WG) and can change the direction of the magnetic moments of small magnetic particles, or groups of particles, embedded in the surface of the disk. If the embedded particles are embedded in such a way that their magnetic moments are perpendicular to the disk surface and can be switched up and down relative to the plane of that surface, then you have what is called perpendicular magnetic recording (PMR). The perpendicular arrangement produces a more densely packed region for magnetic recording.
Perpendicular magnetic recording (PMR) heads have made it possible to extend the increase in the recording density of hard disk drives (HDD) beyond 100 Gb/in2 (100 gigabytes per square inch) However, even using PMR heads, it is difficult to extend the density beyond 1 Tb/in2 due to thermal instabilities and the media's super-paramagnetic limit (the inability to maintain a stable domain structure). In order to achieve a higher recording density, a new technology has been developed: Thermally Assisted Magnetic Recording (TAMR). Briefly, the media that are now used to record at these ultra-high densities must have extremely high coercivities so that data, once it is recorded, can remain stable even when subjected to thermal effects. Unfortunately, the high coercivities required to maintain the data once it is recorded, also makes it difficult for the small PMR heads to provide the necessary flux to actually record that data. One way to record on highly coercive media, is to heat the recording media during the actual recording process so that it reaches its Curie temperature, temporarily reducing its coercivity and then to record the data on the heated surface. When the surface cools, the coercivity is restored to its ambient value and the recorded data is thermally stabilized.
A typical TAMR recording apparatus is furnished with a PMR read/write head configured to transfer optical energy to the surface of a magnetic recording disk having high coercivity and, for the TAMR operational portion, a laser diode to provide optical energy in the form of optical radiation, an optical waveguide to transfer that radiation towards the ABS of the head where it gets close to the recording surface, and a plasmon near-field generator located near that ABS. The plasmon generator is a device that receives the optical radiation from the waveguide, converts it to plasmon modes by electromagnetic coupling and then transfers energy from the plasmon near-fields to a small region of the recording media through the write head portion of the PMR read/write head. The localized near-field energy appears as a near-field spot at the tip of the plasmon generator's air bearing surface (ABS), which is located just below the trailing edge side of the magnetic pole tip. This tiny near field spot, which is not subject to diffraction effects, induces a very localized temperature rise in the recording media to assist the magnetic writing. At the same time, however, the near-field energy induces a very sharp or localized thermal protrusion on the recording head that causes many undesirable issues that should be dealt with. It will be the object of this disclosure to deal with certain of those issues.